Page 1006 - 5G Basics - Core Network Aspects

2 Transport aspects

The LCL of the FTU transceiver shall be greater than or equal to 38 dB in the frequency band up to 12 MHz.
The LCL above 12 MHz is for further study. The termination impedance of the transceiver for LCL
measurement shall be RV = 100 Ohm. The LCL shall be measured at the U-O2 (U-R2) interface. LCL shall be
measured in the frequency band between the lower of the lowest pass-band frequency in the upstream
and downstream directions and Fmax.
NOTE 1 – The equipment balance should be better than the anticipated access network balance in order to minimize
the unwanted emissions and susceptibility to external RFI.
NOTE 2 – FTU performance may benefit from even higher balance. Where subject to repetitive electrical impulse
noise, systems operating at frequencies where the cable balance may be 50 dB could be limited in capacity by a 38 dB
balance.
NOTE 3 – The required LCL may be increased in a future revision of this Recommendation.
NOTE 4 – LCL requirements may be extended in a future revision of this Recommendation, to include dynamic balance
requirements to include perturbations due to active to quiescent impedance state changes in low power link states
driven by fluctuating traffic demand.
14.1.2 Common mode port impedance

For further study.

14.2 Differential port impedance
The port impedance at the U reference point of an FTU-R at a given frequency and point in time is defined
as Z(f,t).

The measurement of Z(f,t) shall be taken separately:
– over the time interval when the transceiver is transmitting (symbol positions from 0 to Mus-1,
including quiet symbol transmissions) resulting in Z_TX(f,t), and

– over the time interval when the transceiver is receiving (symbol positions from 0 to Mds-1)
resulting in Z_RX(f,t)

At any given frequency f between ftr1 and ftr2 as defined in [ITU-T G.9700], and for any set (t1, t2) of a
time interval the Z_TX(f, t) shall satisfy:

Z_TX(f, t1)  1  . 0 20
Z_TX(f, t2)
At any given frequency f between ftr1 and ftr2 as defined in [ITU-T G.9700], and for any set (t1, t2) of a
time interval the Z_RX(f,t) shall satisfy:
Z_RX(f, t1)  1  . 0 20
Z_RX(f, t2)

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